• Tribology and Lubricants
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• 제33권3호
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• pp.92-97
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• 2017

The understanding of the friction characteristics of micro-textured surface is of great importance to enhance the tribological properties of nano- and micro-devices. We fabricate rectangular patterns with submicron-scale structures on a Si wafer surface with various pitches and heights by using a focused ion beam (FIB). In addition, we fabricate tilted rectangular patterns to identify the influence of the tilt angle ($45^{\circ}$ and $135^{\circ}$) on friction behaviour. We perform the friction test using lateral force microscopy (LFM) employing a colloidal probe. We fabricate the colloidal probe by attaching a $10{\pm}1-{\mu}m$-diameter borosilicate glass sphere to a tipless silicon cantilever by using a ultraviolet cure adhesive. The applied normal loads range between 200 nN and 1100 nN and the sliding speed was set to $12{\mu}m/s$. The test results show that the friction behavior varied depending on the pitch, height, and tilt angle of the microstructure. The friction forces were relatively lower for narrower and deeper pitches. The comparison of friction force between the sub-micro-structured surfaces and the original Si surface indicate an improvement of the friction property at a low load range. The current study provides a better understanding of the influence of pitch, height, and tilt angle of the microstructure on their tribological properties, enabling the design of sub-micro- and micro-structured Si surfaces to improve their mechanical durability.

• Journal of Welding and Joining
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• 제32권3호
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• pp.60-67
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• 2014

The ability of electronic packages and assemblies to resist solder joint failure is becoming a growing concern. This paper reports on a study of high speed shear energy of Sn-4.0wt%Ag-0.5wt%Cu (SAC405) solder with different electroless Ni-P thickness, with $HNO_3$ vapor's status, and with various pre-conditions. A high speed shear testing of solder joints was conducted to find a relationship between the thickness of Ni-P deposit and the brittle fracture in electroless Ni-P deposit/SAC405 solder interconnection. A focused ion beam (FIB) was used to polish the cross sections to reveal details of the microstructure of the fractured pad surface with and without $HNO_3$ vapor treatment. A scanning electron microscopy (SEM) and an energy dispersive x-ray analysis (EDS) confirmed that there were three intermetallic compound (IMC) layers at the SAC405 solder joint interface: $(Ni,Cu)_3Sn_4$ layer, $(Ni,Cu)_2SnP$ layer, and $(Ni,Sn)_3P$ layer. The high speed shear energy of SAC405 solder joint with $3{\mu}m$ Ni-P deposit was found to be lower in pre-condition level#2, compared to that of $6{\mu}m$ Ni-P deposit. Results of focused ion beam and energy dispersive x-ray analysis of the fractured pad surfaces support the suggestion that the brittle fracture of $3{\mu}m$ Ni-P deposit is the result of Ni corrosion in the pre-condition level#2 and the $HNO_3$ vapor treatment.

• 대한기계학회논문집A
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• 제31권5호
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• pp.550-555
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• 2007

The effective fracture toughness testing of materials intended for application in Micro Electro Mechanical Systems (MEMS) devices is required in order to improve understanding of how micro sized material used in device may be expected to perform upon the micro scale. ${\gamma}$-TiAl based materials are being considered for application in MEMS devices at elevated temperatures. Especially, in Alloy 4, both ${\alpha}_2$ and ${\gamma}$ lamellae were altered markedly in 3,000 h, $700^{\circ}C$ exposure. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. Parallel decomposition of coarse ${\alpha}_2$ into bunches of very fine (${\alpha}_2+{\gamma}$) lamellae. The materials were examined 2 types Alloy 4 on heat exposed specimen($700^{\circ}C$, 3,000 h) and no heat exposed one. Micro sized cantilever beams were prepared mechanical polishing on both side at $25{\sim}30{\mu}m$ and electro final stage polishing to observe lamellar orientation of same colony with EBSD (Electron Backscatter Diffraction Pattern). Through lamellar orientation as inter-lamellae or trans-lamellae, Cantilever beam was fabricated with Focused Ion Beam(FIB). The directional behavior of the lamellar structure was important property in single material, because of the effects of the different processing method and variations in properties according to lamellar orientation. In MEMS application, it is first necessary to have a reliable understanding of the manufacturing methods to be used to produce micro structure.

• Journal of Welding and Joining
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• 제33권3호
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• pp.47-53
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• 2015

By the trends of electronic package to be more integrative, the fine Cu trace pitch of organic PCB is required to be a robust design. In this study, the short circuit failure mechanism of PCB with a Cl element under the Temperature humidity bias test ($85^{\circ}C$/85%RH/3.5V) was examined by micro-structural study. A focused ion beam (FIB) and an electron probe micro analysis (EPMA) were used to polish the cross sections to reveal details of the microstructure of the failure mode. It is found that $CuCl_x$ were formed and grown on Cu trace during the $170^{\circ}C$/3hrs and that $CuCl_x$ was decomposed into Cu dendrite and $Cl_2$ gas during the $85^{\circ}C$/85%RH/3.5V. It is suggested that Cu dendrites formed on Cu trace lead to a short circuit failure between a pair of Cu traces.

• 대한금속재료학회지
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• 제46권2호
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• pp.58-64
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• 2008

Surface-void defects observed on the galvannealed(GA) steel sheets in Interstitial-free high-strengthened steels containing Si and Mn have been investigated using the combination of the FIB(Focused Ion Beam) and FE-TEM(Field Emission-Transmission Electron Microscope) techniques. The scanning ion micrographs of cross-section microstructure of defects showed that these defects were identified as craters which were formed on the projecting part of the substrate surface. Also, those craters were formed on the Si or Mn-Si oxides film through the whole interface between galvannealed coating and steel substrate. Interface enrichments and oxidations of the active alloying elements such as Si and Mn during reduction annealing process for galvanizing were found to interrupt Zn and Fe interdiffusion during galvannealing process. During galvannealing, Zn and Fe interdiffusion is preferentially started on the clean substrate surface which have no oxide layer on. And then, during galvannealing, crater is developed with consumption of molten zinc on the oxide layer.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.167-170
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• 2005

The two-dimensional (2D) and three-dimensional (3D) diamond-like carbon (DLC) stamps for ultraviolet nanoimprint lithography (UV-NIL) were fabricated using two kinds of methods, which were a DLC coating process followed by the focused ion beam (FIB) lithography and the two-photon polymerization (TPP) patterning followed by nano-scale thick DLC coating. We fabricated 70 nm deep lines with a width of 100 nm and 70 nm deep lines with a width of 150 nm on 100 nm thick DLC layers coated on quartz substrates using the FIB lithography. 200 nm wide lines, 3D rings with a diameter of $1.35\;{\mu}m$ and a height of $1.97\;{\mu}m$, and a 3D cone with a bottom diameter of $2.88\;{\mu}m$ and a height of $1.97\;{\mu}m$ were successfully fabricated using the TPP patterning and DLC coating process. The wafers were successfully printed on an UV-NIL using the DLC stamp. We could see the excellent correlation between the dimensions of features of stamp and the corresponding imprinted features.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.135-138
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• 2005

현재 널리 상용되어 있는PDP는 3전극 변방전형이다. 3전극 면장전형 PDP는 주방전이 유전체 아래에 서로 평행하게 위치하고 있는 ITO투명전극 사이에서 발생한다. 따라서 방전시의 전기장은 MgO 보호막 위에서 아치형태로 형성되게 된다. 플라스마 방전 시 전자에 의해 이온화된 이온 입자들은 전기장에 의해 그 방전경로가 정해지게 된다. 물론 전기장은 표면에서 수직이지만 전기장에 의해 가속되어진 이온입자들은 MgO 보호막에 기울어져서 입사하게 된다. 따라서 플라스마 방전시의 이온들의 MgO 보호막으로의 입사각은 매우 다양하다. $\gamma$-FIB (Focused ion beam) 시스템은 이온입사에 의한 물질의 이차전자방출계수 측정에 효과적인 장비이다. 본 실험은 이러한 $\gamma$-FIB 시스템을 이용하여 다양한 각도로 입사하는 이온빔에 의한 MgO 보호막의 이차전자방출계수를 측정하였다. 또한 이온화 에너지가 다른 여러 종류의 불활성 기체를 사용하여 이온의 입사하는 각도에 따른 MgO 보호막의 일함수를 측정하였다. 이온빔의 입사각은 각각 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 변화시키면서 이차전자방출계수 및 일함수를 측정하였다. 이러한 실험을 통해 입사각이 클수록 이차전자방출계수는 증가하고 일수는 감소하는 것을 확인 할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.617-620
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• 1999

In this study, the polarization e(fecal and the birefringence effect of amorphous germanium (a-Ge) thin films were investigated by using linearly polarized He-Ne laser beam. The a-7e thin films were deposited on the quarts substrate by plasma enhanced chemical vapor deposition (PECVD) and thermal vacuum evaporation In order to obtain the optimum grating arrays, inorganci resists such as Si$_3$N$_4$ and a-Se$_{75}$ Ge$_{25}$ , were prepared with the optimized thickness by Monte Carlo (MC) simulation. As the results of MC simulation, the thickness ofa-Se$_{75}$ Ge$_{25}$ resist was determined with Z$_{min}$ of 360$\AA$ . The resists were exposed to Ga$^{+}$-FIB with accelerating energies of 50 keV, developed by wet etching, and a-Ge thin film was etched by reactive ion-etching (RIE). Finally, we were obtained grating arrays which grating width and linewidth are 0.8${\mu}{\textrm}{m}$, respectively and we studied the polarization and birefringence effect in transmission grating array made of high refractive amorphous material, and the applicability as waveplates and polarizers in optical device.e.e.

• 한국정밀공학회지
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• 제31권12호
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• pp.1101-1106
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• 2014

Hybrid manufacturing technology has been advanced to overcome limitations due to traditional fabrication methods. To fabricate a micro/nano-scale structure, various manufacturing technologies such as lithography and etching were attempted. Since these manufacturing processes are limited by their materials, temperature and features, it is necessary to develop a new three-dimensional (3D) printing method. A novel nano-scale 3D printing system was developed consisting of the Nano-Particle Deposition System (NPDS) and the Focused Ion Beam (FIB) to overcome these limitations. By repeating deposition and machining processes, it was possible to fabricate micro/nano-scale 3D structures with various metals and ceramics. Since each process works in different chambers, a transfer process is required. In this research, nanoscale 3D printing system was briefly explained and an alignment algorithm for nano-scale 3D printing system was developed. Implementing the algorithm leads to an accepted error margin of 0.5% by compensating error in rotational, horizontal, and vertical axes.

• Nuclear Engineering and Technology
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• 제46권2호
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• pp.147-158
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• 2014

In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, different U-7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM). Specifially, samples from irradiated U-7Mo dispersion fuel elements with pure Al, Al-2Si and AA4043 (~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U-7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U-7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with Al-Si matrices.